An Integrated Approach To Optimize Bottomhole-Pressure-Drawdown Management for a Hydraulically Fractured Well Using a Transient Inflow Performance Relationship

Abstract

SummaryThe purpose of this paper is to determine the optimal strategy of bottomhole-pressure (BHP) drawdown management in a hydraulically fractured well with pressure-sensitive conductivity to remain conductive while maintaining a high enough drawdown to maximize the estimated ultimate recovery (EUR). In this work, a novel permeability-decay coefficient accounting for dynamic conductivity effect (DCE) is proposed to represent the pressure sensitivity in a fracture on the basis of experimental results. Using an existing method, the constant/variable BHP conditions and the hydraulic fractures with DCE are considered in the model. Model verification is performed by comparing with the solutions from the numerical method. Then, the mechanism of fracture closure and its effect on production performance are investigated using the semianalytical solution, and the interplay between pressure drawdown and productivity loss is captured by generating a set of type curves for the transient inflow performance relationship (TIPR).Next, an easy-to-use approach is developed to find the optimal path of BHP decline vs. time, and the practical optimal drawdown is calibrated by capturing the time-lapse behavior, with consideration of the effect of production history on TIPR. It is found that if the relation of decay coefficient and pressure is a linear function, there will be a reversal behavior on TIPR as BHP drawdown increases. That is to say, an operating point exists on the TIPR curves, beyond which the production rate decreases; otherwise, the production rate increases. The operating point is defined as the optimal BHP drawdown at a given time, and the optimal profile of BHP drawdown is achieved by integrating operating points on TIPR curves corresponding to different times. Subsequently, a synthetic case generated by a coupled-geomechanical/reservoir simulator is defined to demonstrate that an optimal BHP-drawdown schedule developed by the semianalytical approach has the ability to enhance ultimate recovery by reducing the effective stress on the stress-sensitive fracture while maintaining the well productivity.